Method of making synthetic paper

ABSTRACT

A laminated structure forming a synthetic paper made of a base or backing film layer made of a thermoplastic resin in a biaxially oriented state. A paper-like film layer is laminated to the base film layer and comprises a thermoplastic resin having 0.5 to 65% by weight of particles of a fine, inorganic filler dispersed in the resin thereof substantially uniformly. The paper-like film layer is in an uniaxially oriented state and has microvoids dispersed therein formed by stretching the laminated films in a heated state. The microvoids comprise microvoids open to a surface of the paper-like film layer free of the base film layer and include microvoids, open and closed, distributed in the paper-like film layer defining therein a cellular, fibrous structure. The two films are formed from thermoplastic resinous compositions in which the components of each composition are well admixed and particles of a fine filler are uniformly distributed in the thermoplastic resin of the paper-like film layer to obtain, as much as possible, microvoids distributed therein uniformly. After the base film layer is formed, it is stretched in a heated state in a machine for longitudinal direction to orient the film uniaxially. The paper-like layer is laminated under pressure on one surface of the base film layer while in a melted state and the resulting laminated structure is stretched transversely to at least 2.5 times the original transverse dimension of the portion of film being stretched between grippers of a stretching machine. This orients the base film layer biaxially and the paper-like film layer uniaxially. The stretching must be sufficient for the stretching and particles of filler to develop microvoids in the paper-like film layer rendering it a cellular and fibrous structure. This application is a continuation of application Ser. No. 349,961, filed Apr. 11, 1973, now abandoned; which is a division of application Ser. No. 197,757, filed Nov. 11, 1971, now abandoned; which is continuation-in-part of application Ser. No. 809,629, filed Mar. 21, 1969, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates generally to a laminated structure made of amultiplicity of laminated films and more particularly to a syntheticpaper and the method of making the same.

DESCRIPTION OF THE PRIOR ART

The term synthetic paper as used herein refers to a paper-like laminarstructure made in the form of thin sheets or films of synthetic resinousmaterial employed for various uses, such as writing and printing, asdistinguished from natural cellulose paper.

Synthetic papers made of thermoplastic resin or papers coated withpolymeric emulsions are known for use in writing, printing and the usualuses to which natural cellulose paper is used. Moreover, it is known toorient thermoplastic film laminated structures under elevatedtemperature conditions in a transverse direction to form homogeneousoriented film products having excellent physical and optical properties,such as are shown in U.S. Pat. No. 3,380,868. Polymeric film structureshaving a matte-finish and a cellular structure are also known. Thefinish is produced in these films by a filler which roughens the surfaceupon stretching of the film and renders the film receptive to marking bysuch instruments as a pencil, crayon, ball point pen and the like.Typical of these films is the film disclosed in U.S. Pat. 3,154,461.Laminates comprising layers of oriented films of thermoplastic materialsin which at least one of the outermost layers of film contains asuitable inert additive are also known. The laminates of this type areparticularly of use as films which may be written on by a pencil orcrayon. Laminates of this type are disclosed in U.S. Pat. No. 3,515,626.

In the known oriented films composed of thermoplastic materials andlaminates thereof no attempt has been made to develop microvoids thereinopen to the surface of the film for better adherence of ink or printingmaterials thereon nor a distribution of the microvoids providing acellular, fibrous structure in a paper-like film layer, nor such adistribution of voids relative to the whole paper-like film that thefeel of cellulose paper of the same thickness is imparted thereto,having a specific gravity less than a pulp cellulose paper, improvedreception as to ink, improved printability, opacity and strengthrelative to the known cellulose pulp paper.

SUMMARY OF THE INVENTION

It is a principal object of this invention to provide a synthetic paperor paper-like laminate structure, in the form of sheets of film, whichhas a specific gravity less than natural cellulose paper and improvedreceptivity to ink, improved printability, opacity and strength.

Another object is to provide a new and improved synthetic paper whichhas no fly ash when burned and low calorific content thereby reducingpollution.

Still another object is to provide a synthetic paper from which paperproducts such as writing paper, envelopes, bags, cups, wrappers and thelike can be constructed.

Another object is to provide a strong synthetic paper that has excellentfolding endurance in that it may be folded and unfolded along a foldthousands of times without degradation and rupture.

Another object is to provide a synthetic paper that has greater tensilestrength and burst strength than natural cellulose paper of the samethickness as well as known synthetic papers.

Still another object of the present invention is to provide a syntheticpaper that has excellent waterproof qualities and dimensional stabilityonce subjected to humidity.

Another object is to provide a new and improved method of producing anew and improved synthetic paper.

The synthetic paper according to the invention comprises, a laminatedfilm structure having a base film layer and a paper-like film layerlaminated thereto. The base film layer is a film made of a thermoplasticresin which may have 0 to 20% by weight of a fine inorganic fillerdispersed in the resin and is in a biaxially oriented state. Thepaper-like film layer is likewise made of a thermoplastic resin having0.5 to 65% by weight of a fine inorganic filler dispersed in the resinthereof substantially uniformly and is in an uniaxially oriented state.Microvoids are formed on and in the paper-like film layer and dispersedtherein such that open cells or microvoids open to a surface thereoffree of the base film layer and elongated microvoids are distributed inthe paper-like film layer with fibrous-like portions of the resin amongthe microvoids to define a cellular, fibrous structure.

The method according to the invention provides for admixing theconstituents for making a base film layer principally constituting athermoplastic resin which may or may not be provided with a filler. Thecomposition is formed into a base film and uniaxially oriented in amachine or longitudinal direction. A second thermoplastic film layercomprising therein 0.5 to 65% by weight particles of a fine, inorganicfiller dispersed uniformly in the resin thereof substantially uniformlyis laminated onto the base film layer and the resulting laminatedstructure is uniaxially oriented in a transverse direction so that thebase film layer is biaxially oriented and the second film layer is in auniaxially oriented state. The stretching is at least 2.5 times theoriginal dimension of the transverse portion of the laminated structurebeing stretched so that the stretching in conjunction with the particlesof fine filler develops within this second film layer microvoids, opento a surface thereof free from the base film and distributed in theresin to define therein a cellular, fibrous structure so that the secondfilm becomes a paper-like film layer and the resulting laminate is asheet of synthetic paper-like material or synthetic paper usable forwriting or printing thereon with known instrumentalities and for makingproducts of a type made from cellulose paper. The microvoids are atleast 10% of the whole of the volume of the paper-like sheet or film andpreferably should not exceed 65%.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of a paper-like laminated structure orsynthetic paper according to the invention will be better understood inconjunction with the specification and appended claims and the drawingsin which:

FIG. 1 is a cross-section view diagrammatically illustrating a syntheticpaper according to the invention;

FIG. 2 is an elevation view of a diagram of an apparatus formanufacturing the synthetic paper in FIG. 1;

FIG. 3 is a plan view of a photomicrograph of a paper-like layer ofsynthetic paper according to the invention;

FIG. 4 is a longitudinal section view of a photomicrograph of the paperin FIG. 3;

FIG. 5 is a plan view of a photomicrograph of a printed sheet of plasticsynthetic paper according to the prior art;

FIG. 6 is a plan view of a photomicrograph of a printed sheet of paperaccording to the invention;

FIG. 7 is a diagram or plot illustrating the percentage of voids asrelated to the stretching operation;

FIG. 8 is a perspective view of a bag made of synthetic paper accordingto the invention;

FIG. 9 is a perspective view of an envelope made of synthetic paperaccording to the invention;

FIG. 10 is a perspective view of wrapper paper made of synthetic paperaccording to the invention; and

FIG. 11 is a plan view of an embossed wallpaper made of synthetic paperaccording to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The synthetic paper according to the invention is constructed as amiltiple-layer or multi-layer sheet laminate 1, comprising a base filmlayer 2 made of a thermoplastic resin on a surface of which is adheredor laminated thereon a paper-like film layer 3 made of a thermoplasticresin mixed with particles of a fine inorganic filler within a range of0.5 to 65% by weight. The synthetic paper may be made solely of the twolayers described and may include a second paper-like film layer 5adhered to or laminated to the base film layer on an opposite surface tothat to which the first paper-like film layer 3 is adhered.

The base film layer 2 imparts the physical strength characteristics ofthe synthetic paper according to the invention as herein described. Thepaper-like film layers 3,5 provide improved surfaces on which writingand printing may be accomplished with the known writing and printinginstrumentalities as hereinafter described.

The base film layer 2 and paper-like film layer 3 are formed fromcompositions which are later herein described in detail. The base filmlayer thermoplastic resin, with whatever additives have been addedthereto, is fomed by an extruder 7 which is of a single screw typehaving an L/D ratio over twenty-eight. The extrusion of the film 2 isthrough a film-forming die 8 having a uniformity index over 0.9. Thefilm 2 is delivered longitudinally over a set of rolls 10, 11 and passesthrough the nip of the rolls where its uniformity of thickness ismaintained at a desired thickness as hereinafter disclosed. The film isdelivered over guide rolls 12,13 to a longitudinal stretching zone ormachine 15 which uniaxially orients the film in the longitudinal ormachine direction. The film passes over a heating roll 15a, or it may beotherwise heated by infra red heating devices, not shown. The heatedthermoplastic film is stretched by two stretching rolls 15b, 15c. Thefilm is stretched at least 1.3 times its longitudinal dimension toorient the thermoplastic resin therein and improve the physical strengthcharacteristics of the film that will become the base layer film 2. Thestretched film is cooled by a cooling roll 15d. The uniaxially orientedbase layer film is advanced longitudinally over guide rolls 17,18 to aset of laminating rolls 20,21 where it is laminated to a secondthermoplastic film, which will become the film layer 3 describedhereinafter as to composition and characteristics, extruded by afilm-forming extruder 23 which is diagrammatically illustrated and is avent-type extruder having an L/D ratio on the order of the firstdescribed extruder and a die with a similar uniformity index. Thelaminating takes place in the nip of the laminating rolls 20,21 at apressure avoiding the formation of undulations in the surface of thefilms while maintaining pressure sufficient to obtain a strong bondbetween the two laminated film layers 2,3.

The double film or two-layer laminate is advanced longitudinally overguide rolls 25,26,27 and is advanced to a second set of laminating rolls30,31 adjacent which is disposed a third extruder 33 of the same type asthe second extruder 23 delivering a thermoplastic resin film,constituting the third film layer 5, laminated under pressure to asurface of the base film opposite to the first lamination of the firstfilm thereon. The three-ply laminate 1 is advanced longitudinally overguide rolls 35,36,37 as illustrated where cooling takes place and isadvanced to a second stretching apparatus 39 divided into three zones. Afirst zone is a pre-heating zone where the three-layer laminate isheated, for example, with hot air heating devices, to a temperature inthe order of 140° to about 180° C. and is then stretched in a transversedirection at least in the order of 2.5 times the original dimensions ofthe portions of the laminate between the stretching grippers of astretching device in the second or stretching zone. The laminate isadvanced from the stretching zone to a third zone or setting zone inwhich the laminate is reduced in temperature to about 120° to 160° C.The temperature of the laminate in the stretching zone is in the orderof 140° to 170° C.

The set laminate 1 may then be delivered to a take-up apparatus,however, the method of the invention provides for a surface treatment toimprove the adherence of ink to the two outermost film layers 3,5 bypolarizing the two outermost films. It has been found that the adherenceof ink can be improved by applying to the surface of the outermost filmlayers a corona discharge treatment accomplished by electrodes 41,42 onopposite sides of the laminate to which a voltage of 3000 to 30,000volts is applied with a plate current of 0.5 to 5 amperes. Treatment isaccomplished by maintaining the clearance between the laminate and theelectrodes 41,42 constant. Accordingly stabilizing rolls 44,45 maintainthe film laminate 1 and electrode clearance accurately, it beingunderstood that the electrodes are disposed immediately adjacent to thestabilizing rolls downstream thereof and extend transversely of the filmlaminate 1.

The invention provides for a composition of the outermost layers of thelaminate to provide paper-like layers on which writing and printing cantake place with known instrumentalities. The composition of thepaper-like layers is described hereinafter, however the composition ofthe thermoplastic resin with the controlled filler content and minimumsize of filler particles constituting 0.3 microns and the uniformdistribution of the filler provides a composition in which microvoidscan be controllably developed by the transverse stretching of thelaminate. The microvoid formation is a function of the size of fillerparticles, the extent of stretching, and the filler content which is inthe order of 0.5% to 65% by weight preferably in the order of 20% byweight and more particularly 25% by weight of the whole of thecomposition from which the paper-like layers 3,5 are formed.

The stretching of the laminate 1 must be sufficient to develop aninternal mechanism within the outermost films during the stretching inwhich inorganic filler particles 50, in each of the outermost filmlayers 3,5 coact with the stretching to develop microvoids 51 in thefilm layers. The transverse stretching must be at least 2.5 times theoriginal dimension as before described. Stretching of seven times thedimension and even higher, for example, up to sixteen times, has yieldedsuitable voids. Thus as the stretching takes place, stresses developabout the uniformly dispersed filler particles 50 and microvoids orcells 51 are developed. Some cells 52 are formed next adjacent to thesurface of the outermost films 3,5 free of the base film layer 2. Thesecells or voids 52 are open to the surface and in communication therewithas illustrated in FIG. 3. The transverse orientation of the paper-likelayers or films 3,5 results in formation of microvoids 51 internally ofthe film structure as illustrated in FIG. 4. The distribution of theinternal microvoids 51 is such that portions 55 of the resin among themicrovoids are fibrous in structure as clearly shown in FIG. 4. Theinternal cells or microvoids 51 may be independent, and some willcommunicate with others. Generally each microvoid 51 has internallythereof a filler particle 50 effecting the formation of a microvoid. Thefiller particles generally are in contact with two opposite sides orboundaries 50a,50b of the resin within which the microvoid is formed asis clearly seen in FIG. 4. The microvoids 52 on the surface of thepaper-like film layers 3,5 provide the synthetic paper or laminate witha better receptiveness to ink than other synthetic paper or film. Thesurface likewise has the "feel" of natural cellulose papers, and thesurface is improved for writing thereon with known instrumentalitiessuch as a pencil, crayon, ball point pen and the like.

The microvoids 51 formed interiorily of the outermost film layers reducethe density and specific gravity of these layers so that the resultinglaminate or synthetic paper 1 is much lighter than known syntheticwriting films and papers including coated natural cellulose papers andart paper. The fibrous, cellular structure of the outer films 3,5provides a cushionability improving the printing and ink transfer duringprinting with the known techniques. Accordingly the ink transfer to thesurface on the printed areas is substantially uniform as illustrated inFIG. 5 as compared with known plastic coated paper as illustrated inFIG. 6 and other synthetic films and papers.

The microvoid formation and particularly the surface microvoids improvethe light reflective characteristics of the synthetic paper according tothe invention so that the whiteness and opacity is better than that ofnatural cellulose papers and synthetic films and papers. The improvedwhiteness and opacity improves the ability of reproducing the desiredprinted image.

These improved characteristics in conjunction with the improvedcushionability and ink receptiveness result in the improved printing andthe quality thereof mentioned heretofore. The ink dots 67 of theprinting on a printed paper 69 according to the invention aredistributed uniformly on the surface and spaces or gaps, of the typeshown at 70,71 on a known coated paper in FIG. 6, are avoided. Theuniformity of the printing assists in the reproduction of the desiredimage.

The reduced density and cellular structure throughout the syntheticpaper 1 improves its anti-pollution characteristic in that there is areduction in solid matter and the voids provide spaces and areas readilyaccessible to air so the paper will burn more readily with less releaseof heat and less calorific value. The synthetic paper 1 will burnwithout smoke and fly ash in that complete combustion takes paper andthe ashes remain in the container within which the burning takes place.

The base film layer 2 is principally a thermoplastic resin. Specificallypolyolefin resins such as homopolymers and copolymers of, for example,ethylene, propylene and butene-1, polyamide resins; polyester resin suchas polyethylene terephthalate polyvinyl resin such as homopolymers andcopolymers of vinyl chloride; and polyvinylidene resins such ashomopolymers and copolymers of vinylidene chloride and homopolymers andcopolymers of styrene can be used singly or as a mixture thereof.Moreover, auxiliary materials such as a stabilizer, plasticizer, fillerand pigment may be contained in the base film layer material resinwithin its stretching range as necessary. When less than 20% by weightof a filler is blended into the base layer film resin some favorableresults can be obtained. These results are an improved whiteness,opacity, stiffness and toughness of the resulting synthetic paper.Moreover, the surface of the base film layer 2 becomes coarse andadhesion of the other two films thereto is greatly improved.

An orientable thermoplastic resin is used for the paper-like film layers3,5 and may be the same or a different resin selected from the group ofthe above-mentioned resins used in the base film layer. When a heatsealing characteristic is desired, the softening point of the paper-likefilm layer must be less than that of the base film layer resin. Forexample, in the event that the base film layer is made of a homopolymer,and the paper-like film layer is made of a copolymer containing amonomer which is a component unit of the homopolymer, in the base filmlayer the resulting paper-like layer will have a lower softening pointthan that of the base layer. Under these conditions a favorable heatsealing characteristic can be developed in the paper and heat sealingcan be carried out free from shrinkage of the base film layer.

The selection of the resins must be such that the resins in thedifferent layers have a sufficient adhesiveness with respect to the basefilm layer so that lamination can be carried out effectively. The use ofa filler in the base film layer develops microvoids on the surfacethereof improving the adhesion of the paper-like layers thereto.Moreover, an anchor coat can be applied to the base film layer toimprove the adhesion of the laminate film layers, for example using apolyisocyanate or a polytitanate. The resin for the paper-like layer mayalso contain suitable auxiliary materials as in the case of the baselayer resin.

The paper-like film layer resin contains particles of a fine inorganicfiller as listed hereinafter. Care must be taken in selecting the fillerso that it is a filler which does not discolor due to decomposition atelevated temperatures which are applied in the course of making thesynthetic paper according to the invention. Examples of suitableinorganic fillers for the paper-like film layers are: clay, talc,asbestos, gypsum, barium sulfate, calcium carbonate, magnesium oxide,diatomaceous earth and silicon oxide particles used either singly or asa mixture of two or more of these fillers. The filler must be finefiller, for example, of a grain size of approximately 0.5 - 30 micronsbut the particles should be no less than 0.3 microns in order to developthe microvoids as heretofore described. The paper-like film layerscontain 0.5% to 65% and preferably 5% to 60% by weight of a fineinorganic filler in the component materials.

As heretofore explained the addition of the inorganic filler in theformation of microvoids and accordingly the lightness, stiffness andtoughness of the paper-like layer are greatly improved. Theprintability, whiteness and the feel of the overall paper are improvedbecause of generation of voids.

The resin of the paper-like film layers is prepared for delivery to thefilm-forming extruders 23,33 by taking 100 parts of the resin andseparating it into two batches. A batch of 90 parts of the resin has thefiller to be added thereto, for example, constituting in the order of 20parts. A master small batch of resin is prepared which constitutes 10parts of the original 100 parts of the resin to which are added anantistatic agent, the stabilizer as hereinafter described and adispersing agent in small amounts, for example, in the order of 0.3 to 1percent. The dispersing agent assists in obtaining a uniformdistribution of the inorganic filler particles. The two separate batchesare independently mixed in a Henshel mixer and after mixing of thebatches the two batches are then mixed together in a Henshel mixer. Theresulting mixture of the two batches is then delivered to a twin screwextruder in order to improve the uniformity of the mixture and theuniformity of distribution of the inorganic filler throughout thecomposition. The output from the twin screw mixer is the startingmaterial or product pellets which are delivered to the film-formingextruders 23,33 heretofore described with respect to FIG. 2.

The composition used for making the base film layer is treated similarlyto the preliminary steps defined heretofore with respect to the mixingand extruding of the paper-like film layers. However, in the event thatthe filler is of a small amount, for example, 3% to 5% by weight, thematerials are mixed in a single batch in a Henshel mixer and thendelivered to a twin screw extruder where it is pelletized and thestarting material for the film-forming extruder 7 is thus made.

The relation or ratio between stretching and void formation isillustrated in the graph in FIG. 7. The graph illustrates curvesindicating that the stretching and the filler content control the ratioof voids to the whole of the individual paper-like film layers. Therange of the curves illustrate that transverse stretching of at least2.5 times (X 2.5 as shown) will form voids and that the stretching canexceed 15.0 times (X15) the original transverse dimension.

The following lists and tables set forth examples of the components usedin preparing the several film layers and the ratios and manufacturingconditions:

RESINS

Pp; polypropylene

Pe; polyethylene

Eva; ethylene-vinyl

Epp; ethylene-propylene-copolymer

Pvc; polyvinyl chloride

Pvdc; polyvinylidene chloride

Ps; polystyrene

Hi/ps; high impact polystyrene

Abs; acrylonitrile butadiene styrene copolymer

FILLERS

Kieselguhr, clay, Ca-carbonate, TiO₂, Barium sulfate, Magnesium oxide.

STABILIZERS

Calcium stearate

Alminum stearate

Zinc stearate

Calcium laurylate

Titanium dioxide

Barium stearate

(TOPANOL) 1,3,5, tris (2-methyl-4hydroxy-5-t-butyl phenol) butane

ANTI-STATIC AGENTS Polyoxy alkyl amine

NYMEEN-S-210 (made by Nippon Oils and Fat Co., Ltd.) C₁₈ H₃₇ N(CH₂ CH₂O)(OH)₂ Tertiary alkylamine; Molecular wt. 1135; Vis. 500 cps

Alliphatic glycerine ester

RESISTAT-PE-132 (made by Deiichi Kogyo Seiyaku Co., Ltd.) mono glycerideof C₁₇ H₃₅ COOH C₁₇ H₃₅ COOCH₂ --CHOH--CH₂ OH molecular weight 358

RESISTAT-PE-139 almost the same kind as above.

Alkyl phosphate

PHOSPHANOL-SM-1 (made by Toho Chemical Industries Co., Ltd.) (RO(CH₂ CH₂O)N)₃ P R= alkyl with carbon number 18.

PHOSPHANOL-NP-10 The same substance as above except R= alkyl with carbonnumber 12.

Alkyl Betaine

LEOSTAT-532 (made by Lion Fat and Oil Co., Ltd.) R((CH₂ CH₂ O)NH)₂ N⁺CH₂ COO.sup. -

DISPERSION AGENTS Polyoxy ethylene alkyl ether

EMULGEN (made by KAO-ATLAS Co., Ltd.) C₁₈ H₃₇ O(CH₂ CH₂ O)_(n) OH n= 10Molecular weight 710

Alkyl phospho esterate

OM-11 (made by Marubishi Petrochemical Co., Ltd.) (RO)₂ P(O)(OX) R=alkyl with carbon number 12-18. X= amine viscosity 500cps boiling point330°C.

Polyoxy alkylamine

NYMEEN-T-210 (made by Nippon Oils and Fats Co., Ltd.) R--N(CH₂ CH₂O)(OH)₂ R= unsaturated alkyl with carbon number approximately 10.

ANCHOR COATING AGENTS Polyisocyanate

EL-250 (made by Toyo Ink Manufacturing Co., Ltd.) polyisocyanate thathas R-NCO

Polytitanate

EL-110 (made by Toyo Ink Manufacturing Co., Ltd.)

    TABLE I      COMPONENTS: BASE LAYER             Other  Ex.       Anti-static     Dispersing  Ingredients No. Resin Parts* Filler Parts Stabilizer Parts     Agent Parts Agent Parts Parts       1 PP 100  clay 5 Ca-stearate 0.3 PHOSPHANOL SM-1 0.1 NYMEEN S-210 0.1         k. 10 TOPANOL 0.1 (Toho-Chem. Inc)  (Nippon Oil and Fat Co, Ltd.) --      2 PP 90 clay 5 Ca-stearate 1.0 PHOSPHANOL SM-1 0.3 NYMEEN S-210 0.3  PE     10   TOPANOL 0.1 (Toho Chem. Inc)  (Nippon Oil & Fat Co. Ltd) -- 3 PP 80     clay 25 Al-stearate 1.0 LEOSTAT-532 0.5 EMULGEN 0.6  Polybutene-     TOPANOL 0.5 (Lion Fat & Oil Co.)  (Kao Atlas Co.)  --  1 10  PE 10 4 PP     80 clay 3 Zn-stearate 0.5 LEOSTAT-532 1.0 EMULGEN  Antiultra vib-     EVA(VA 12%)    TOPANOL 0.1 (Lion Fat & Oil Co.)  (Kao Atlas Co.) 0.5 let     Agent 0.3 5 PE 80   Ca-stearate 1.0 --  --  --  EVA 20 --  TOPANOL 0.1     (VA 15%) 6 PP 90 --  Ca-laurate 0.5 --  EMULGEN 0.5 --  EPP(E 3%) 10     TOPANOL 0.5   (Kao Atlas Co.) 7 PP 90 clay 2 Zn-stearate 0.5 --  EMULGEN     0.3 --  EPP 10 Ca-carbo- TOPANOL 0.3   (Kao Atlas Co.)  (E 15%)  nate 10     8 PP 90 clay 15 Ca-stearate 1.3 --  EMULGEN 0.3 --  EPP(E15%) 10     TiO.sub.2 10 TOPANOL 0.7   (Kao Atlas Co.) 9 PE 100  clay 10 TOPANOL 0.1     --  EMULGEN 0.3 --          (Kao Atlas Co.) 10 PVC 80 barium sul-     Ba-stearate 1.5 --  EMULGEN 1.0 --  PVC-(VC80%) fate 3     (Kao Atlas     Co.)  PVDC 20 clay 2 11 PP 80 clay 1 --    NYMEEN S-210 0.1  PE-terephtha     -     --  (Nippon Oil & Fat Co.)  --  late 20 12 PP 80 Kieselguhr  --     NYMEEN S-210 0.1 --  Polyamide   0.5     (Nippon Oil & Fat. Co.)     (Nylon-6) 20 13 PP 100  --  Ca-stearate 0.5 --  --  -- 14 PP 100  --     Ca-stearate 0.5 --  --  -- 15 PS 100  --  --  --  --  -- 16 PE 100  --     Ca-stearate 0.5 --  --  -- 17 PE 80 clay 1 Ca-stearate 0.5 MYMEEN S-210     0.5 --  --  HI/PS 20 Kieselguhr  TOPANOL 0.3 (Nippon Oil & Fat. Co.)  --      -- 18 PE 80 clay 2 Al-stearate 1.0 RESISTAT PE 132 0.5 --  --  ABS     (A10% 20 Kieselguhr  TOPANOL 0.3 (Daiichi Kogyo Seiyaku)  B 20% and  S     70%)       Weight percent of filler or other components can be calculated by the     following formula:      ##STR1##     *NB- All "parts" are "parts by weight"

    __________________________________________________________________________    TABLE II (a)                                                                  COMPONENTS: PAPER-LIKE LAYER                                                  Ex.                                                                           No.  Resin   Parts*                                                                             Filler   Parts                                                                              Stabilizer                                                                            Parts                                 __________________________________________________________________________    1    PP      100  clay     15   Ca-stearate                                                                           0.5                                                     Kieselguhr    TOPANOL 0.3                                   2    PP      80   clay      5   Ca-stearate                                                                           1.0                                        PE      20                 TOPANOL 0.1                                   3    PP      80   clay     40   Al-stearate                                                                           0.5                                        Polybutene-                TOPANOL 0.5                                        1       10                                                                    EVA(VA  10                                                                    10%)                                                                     4    PP      80   clay     23   Zn-stearate                                                                           0.5                                        EVA(VA12%)   Kieselguhr                                                                             10   TOPANOL 1.0                                                20                                                               5    PVC     100  clay     50   Ca-stearate                                                                           1.0                                                     Ca-carbon-    Ba-stearate                                                                           1.0                                                     ate      80                                                 6    PP      90   clay     70   Ca-laurate                                                                            0.5                                        EPP(E 3%)                                                                             10   Kieselguhr                                                                             40   TOPANOL 0.5                                                     TiO.sub.2                                                                              20                                                 7    PP      30   clay     10   Zn-stearate                                                                           0.3                                        EPP(E 15%)   Ca-carbon-    TOPANOL 0.3                                                70   ate      15                                                 8    PE      80   clay     100  TOPANOL 0.2                                        EPP(E 15%)                                                                            20   Kieselguhr                                                                             50                                                 9    EPP     100  clay     33   TOPANOL 0.1                                        (E 20%)                                                                  __________________________________________________________________________    Ex. Anti-static      Dispersing                                               No. Agent       Parts                                                                              Agent        Parts                                                                            Others                                                                             Parts                               __________________________________________________________________________    1   PHOSPHANOL SM-1                                                                           0.1  NYMEEN S-210 0.7                                                                              --                                           (Toho Chemical Inc.)                                                                           (Nippon Oil & Fat Co.)                                   2   PHOSPHANOL SM-1                                                                           0.3  NYMEEN S-210 1.0                                                                              --                                           (Toho Chem. Inc.)                                                                              (Nippon Oil & Fat Co.)                                   3   PHOSPHANOL SM-1                                                                           0.5  NYMEEN S-210 1.0                                                                              --                                           (Toho Chem. Inc.)                                                                              (Nippon Oil & Fat Co.)                                   4   NYMEEN S-210                                                                              0.3  NYMEEN S-210 0.3                                                                              Antiultra                                    (Nippon Oil & Fat Co.)                                                                         (Nippon Oil & Fat Co.)                                                                        violet                                                                             0.3                                                                      Agent                                    5   NYMEEN S-210                                                                              1.0  NYMEEN S-210 0.5                                                                              --                                           (Nippon Oil & Fat Co.)                                                                         (Nippon Oil & Fat Co.)                                   6   NYMEEN S-210                                                                              0.5  EMULGEN      0.5                                                                              --                                           (Nippon Oil & Fat Co.)                                                                         (Kao Atlas Co.)                                          7   NYMEEN S-210                                                                              0.5  EMULGEN      0.5                                                                              --                                           (Nippon Oil & Fat Co.)                                                                         (Kao Atlas Co.)                                          8   --               --              --                                       9   --               --              --                                       __________________________________________________________________________    TABLE II (b)                                                                  COMPONENTS: PAPER-LIKE LAYER                                                  Ex.                                                                           No.  Resin   Parts*                                                                             Filler   Parts                                                                              Stabilizer                                                                            Parts                                 __________________________________________________________________________    10   PVC     100  clay     100  Ba-stearate                                                                           1.5                                                                   Ca-stearate                                                                           0.5                                   11   PP      80   clay     50   --                                                 PE-terephtha-                                                                 late    20                                                               12   PP      80   clay     80   --                                                 Polyamide                                                                     (Nylon-6)                                                                             20                                                               13   PP      80   clay     80   --                                                 Polyamide    Magnesium                                                        (Nylon-6)                                                                             20   Oxide    20                                                 14   PP      80   clay     70   --                                                 PS      20   Ca-carbon-                                                                    ate      30                                                 15   PS      100  clay     90   --                                                              TiO.sub.2                                                                              10                                                 16   PE      80   clay     70   --                                                 PS      20   Barium sul-                                                                   fate     10                                                 17   PE      80   clay     80   Ca-stearate                                                                           0.7                                        HI/PS   20   Kieselguhr                                                                             30   TOPANOL 0.5                                   18   PE      80   clay     20   Ca-stearate                                                                           0.7                                        ABS     20   Ca-carbon-    TOPANOL 0.5                                                     ate      15                                                 __________________________________________________________________________    Ex. Anti-static      Dispersing                                               No. Agent       Parts                                                                              Agent        Parts                                                                            Others                                                                             Parts                               __________________________________________________________________________    10  --               --                                                       11  RESISTAT PE 132                                                                           0.3  NYMEEN S-210 0.1                                                                              --                                           (Daiichi Kogyo Seiyaku                                                                         (Nippon Oil & Fat Co.)                                   12  "           0.7  "            0.5                                                                              --                                       13  "           0.7  "            0.5                                                                              --                                       14  "           0.7  "            0.5                                                                              --                                       15  "           0.7  "            0.5                                                                              --                                       16  "           0.7  "            0.5                                                                              --                                       17  NYMEEN S-210                                                                              0.5  --              --                                           (Nippon Oil & Fat Co.)                                                    18  NYMEEN S-210                                                                              0.5  --              --                                           (Nippon Oil & Fat Co.)                                                    __________________________________________________________________________     *NB- "parts" are "parts by weight".                                      

                                      TABLE III                                   __________________________________________________________________________    MANUFACTURING CONDITIONS                                                                           PAPER-LIKE LAYER                                         Base Layer           Temperature                                                 MD (Machine                                                                           stretching ratio                                                                        lamin-                                                                            pre-heat-                                                                           stretch-                                                                           set-                                                                             Stretching                                Direction)                                                                            (x) (times initial                                                                      ating                                                                             ing   ing  ting                                                                             Ratio                                  Ex.                                                                              C°                                                                             length)   C°                                                                         C°                                                                           C°                                                                          C°                                                                        (x)                                    __________________________________________________________________________    1. 150     5         260                                                                              160    160  140                                                                              8                                      2. 140     2         300                                                                              160    150  140                                                                              5                                      3. 140     4         250                                                                              160    150  130                                                                              7                                      4. 140     6         250                                                                              150    145  130                                                                              6                                      5. 130     1.3       130                                                                              150    140  120                                                                              4                                      6. 140     5         280                                                                              165    145  140                                                                              5                                      7. 140     5         280                                                                              160    150  140                                                                              8                                      8. 150     4         280                                                                              160    150  140                                                                              7                                      9. 135     3         250                                                                              160    150  140                                                                              2.5                                    10.                                                                              100     5         130                                                                              110    100  85 6                                         145     4         280                                                                              165    160  140                                                                              5                                         145     5         250                                                                              165    160  140                                                                              7                                         140     5         250                                                                              160    150  140                                                                              8                                         140     6         250                                                                              160    150  140                                                                              7                                         100     4         200                                                                              120    110  90 6.5                                       135     6         220                                                                              140    130  130                                                                              5                                         135     7         250                                                                              140    130  130                                                                              8                                         135     5         250                                                                              140    130  130                                                                              4                                      __________________________________________________________________________     Note -                                                                        The transverse stretching speed in a transverse direction in the above        manufacturing conditions was at a speed of 3000 percent per minute. The       stretching speed in a transverse direction may generally be in a range of     2000 percent to about 10,000 percent per minute.                         

                  TABLE IV                                                        ______________________________________                                        THICKNESS OF ARTICLE                                                                   BASE LAYER      PAPER-LIKE LAYER                                              (microns)       (microns)                                            Ex.      82              μ                                                 ______________________________________                                        1.       40              40                                                   2.       50              60                                                   3.       30              10                                                   4.       20              10                                                   5.       30              30                                                   6.       60              20                                                   7.       70              40                                                   8.       30              50                                                   9.       80              60                                                   10.      50              20                                                   11.      20              100                                                  12.      40              50                                                   13.      20              20                                                   14.      20              10                                                   15.      80              70                                                   16.      40              80                                                   17.      40              100                                                  18.      50              30                                                   ______________________________________                                    

                                      TABLE V                                     __________________________________________________________________________    PROPERTIES                                                                             TENSILE      INK       TEAR   FOLDING                                         STRENGTH     TRANS                                                                              INK  STRENGTH                                                                             ENDUR-                                    OPACITY                                                                             MD/TD  SPECIFIC                                                                            FER  AD-  MD/TD  ANCE                                   Ex.                                                                              (%)   (kg.)  GRAVITY                                                                             (g/m.sup.2)                                                                        HESION                                                                             (kg/cm)                                                                              (cycles)                               __________________________________________________________________________    1. 55     9.6/17.6                                                                            0.78  2.1  Δ                                                                            70/60  >150,000                               2. 38    12.5/24.5                                                                            0.85  1.2  Δ                                                                            108/98 >150,000                               3. 38    5.6/9.6                                                                              0.81  3.0  O    65/58  >150,000                               4. 35    3.7/7.3                                                                              0.75  3.0  O    46/43  >150,000                               5. 60     7.2/14.4                                                                            0.68  3.2  O    66/59  >150,000                               6. 89     9.6/17.2                                                                            0.72  3.2  O    108/100                                                                              >150,000                               7. 57    13.0/26.2                                                                            0.77  2.1  Δ                                                                            120/110                                                                              >150,000                               8. 90    13.1/25.6                                                                            0.71  3.4  O    70/62  >150,000                               9. 91    10.1/23.1                                                                            0.78  3.1  O    120/105                                                                              >150,000                               10.                                                                              88     8.4/19.2                                                                            0.72  3.2  O    105/95 >150,000                                  93     14.2/25.0                                                                           0.72  3.1  O    25/22  >150,000                                  92    10.2/20.0                                                                            0.73  3.1  O    50/45  >150,000                                  48    5.8/9.6                                                                              0.69  3.0  O    21/19  >150,000                                  40    4.2/8.2                                                                              0.73  3.1  O    20/18  >150,000                                  92      7.2/15.6                                                                           0.81  2.9  O    85/70  >150,000                                  90    11.5/23.2                                                                            0.78  2.8  O    60/52  >150,000                                  94    10.5/21.3                                                                            0.79  3.1  O    50/40  >150,000                                  87     9.7/17.6                                                                            0.85  2.9  O    70/50  >150,000                                               Natural Cellulose Paper                                       85˜90                                                                            8.9/5.4                                                                              0.8˜1.2                                                                       2.3˜3.5                                                                      0    28/26  1000                                   __________________________________________________________________________     MD - Machine Direction                                                        TD - Transverse Direction                                                     ˜- symbol for "approximately"-                                          O - good                                                                      Δ- fair                                                            

                                      TABLE VI                                    __________________________________________________________________________    FILLER EFFECT IN BASE LAYER*                                                  Filler                                                                        Content                                                                            Stretching Stability                                                                    Tear Strength                                                  (wt. %)                                                                            (without splitting)                                                                     (after stretching)                                                                     Opacity                                                                            Whiteness                                        __________________________________________________________________________    0    good      good     opacity                                                                            whiteness                                        10   good      good     increases                                                                          increases                                                                as   as                                               20   good      good     filler                                                                             filler                                           25   inferior  inferior content                                                                            content                                               (film split)       increases                                                                          increases                                                                ↓                                                                           ↓                                         30   poor      poor     good good                                                  (film split)                                                             __________________________________________________________________________     *Resin = PP                                                                   Filler = Kaolinite clay                                                  

    __________________________________________________________________________    TABLE VII (a)                                                                 EFFECT OF FILLER CONTENT IN PAPER-LIKE LAYER                                            Properties-A           Properties-B                                 Ex.  Filler                                                                             Hardening                   Surface                                 (Resin=                                                                            Content                                                                            time of                                                                             Ink   Ink trans-                                                                          Opacity                                                                            Gloss                                                                              intensity                                                                              Smoothness                     PP)  (wt.%)                                                                             ink(min.)                                                                           adhesion                                                                            fer(g/m.sup.2)                                                                      (%)  (%)  (IGT cm/sec)                                                                           (Beck sec)                     1.   0.5  1000  Δ˜x                                                                     0.8   7    60   360      3000                           2.   5    820   Δ                                                                             1.2   38   45   360      1700                           3.   20   240   O     2.8   88   36   290      1200                           4.   25   200   O     2.9   89   35   280      1150                           5.   30   180   O     3.0   90   34   270      1120                           6.   60   95    O     3.4   94   22   200      800                            7.   65   80    O     3.5   95   20   130      500                            8.   70   70    O     3.5   95   15   55       100                            __________________________________________________________________________    Natural Cel-                                                                  lulose Paper                                                                            50˜250                                                                        0     2.5˜3.5                                                                       3˜40                                                                         100˜200                                                                      100˜1000                          __________________________________________________________________________     Properties A = Improve as filler content                                      Properties B = Decrease as filler content increases                           Beck sec = The higher in value indicates improved smoothness                  Δ = Fair                                                                X = Inferior                                                                  O = Good                                                                      Resin = PP                                                                    Filler = Kaolinite clay                                                      TABLE VII (b)                                                                 EFFECT OF FILLER CONTENT IN PAPER-LIKE LAYER ON VOID FORMATION                                   Properties-A        Properties-B                               Void pro-                              Surface                                portion*                                                                            Filler                                                                            Stretch-                                                                           Harden-                 inten-                                                                             Smooth-                           in pa-                                                                              con-                                                                              ing ex-                                                                            ing             Opa-    sity ness                              per-like                                                                            tent                                                                              tent(x)                                                                            time of                                                                            Ink ad-                                                                            Ink trans-                                                                          city                                                                              Gloss                                                                             (IGT)                                                                              (Beck                         Ex. layer(%)                                                                            (wt%)                                                                             times)                                                                             ink (min)                                                                          hesion                                                                             fer(g/m.sup.2)                                                                      (%) (%) cm/sec)                                                                            cm/sec)                        9.1                                                                              5     5   8    820  Δ                                                                            1.2   38  45  360  1700                          10. 10    20  4    300  Δ                                                                            2.1   57  42  360  1500                          11. 15    20  5    250  O    2.8   88  38  300  1250                          12. 20    25  5    200  O    2.8   89  36  290  1200                          13. 30    35  8    170  O    3.0   92  34  270  1120                          14. 59    60  12   95   0    3.4   94  24  210  1000                          15. 60    63  9    90   O    3.4   95  22  200  800                           16. 65    65  15   80   O    3.5   95  20  130  500                           17. 70    70  15   70   O    3.5   95  15  55   100                           __________________________________________________________________________    Natural Cellulose                                                             Paper              50˜270                                                                       0    2.3˜3.5                                                                       85˜90                                                                       3˜40                                                                        100˜200                                                                      100˜1000                __________________________________________________________________________    *Void Proportion of Paper-like layer is as follows:                            ##STR2##               where V: Void Proportion  Po : Initial Density of                             paper-like layer P: Density of paper-like layer                               after stretching                                      Δ = Fair O = Good Resin = PR Filler = Kaolinite clay and Kieselguhr      ##STR3##                                                                        In the tables above if the tables with a numeral and a letter are          placed one above the other in proper sequence of the examples listed          therein and in a descended order from left to right, an overall view of       the components, manufacturing conditions and resulting characteristics of 

The tables VII (a) and VII (b) indicate the effect of filler on variousproperties of the synthetic paper and provide a comparison with naturalcellulose paper. As can be seen from the tables, the synthetic paperaccording to the invention has improved qualities over paper made fromnatural pulp.

The synthetic papers according to the invention are suitable for use ashigh grade printing paper, for cards, maps, charts, decorative papers,dull finished or mat papers, typing, duplicating, drafting, tracing,writing, drawing, packaging, wrapping, paper boards and the like.

The synthetic paper made according to the invention provides a paperwith sufficient toughness and strength to be used for making bags asshown in FIG. 8 in which a shopping bag 70 is made out of a single sheetof synthetic paper. The sheet is folded in a conventional manner andmade into the bag. The longitudinal seam along the length of the bag andfolds forming the bottom of the bag are bonded by use of an adhesive orbonding agent. Bonding can be effected by heat seals or "welds". Whenheat seals or bonds are effected suitable pressures, times andtemperatures and current values are used as is well known in this art.The bag is provided with handles 75,76 made, for example, of syntheticfilaments anchored to the bag by strips 77,78 of rigid material, forexample paper or cardboard, underlying folds 79,80 at the mouth of thebag.

Not only is the synthetic paper very strong and adequate for this usebut the exterior of the bags may be decorated more clearly with coloredprinted pictures than when using only conventional printing paper. Thusthe pictures are those of a city and mountain scenes and planes, etc.,as desired. The possibility of using heat for forming bonds makes itpossible to manufacture envelopes 81 as shown in FIG. 9 in which all ofthe cutting, folding and bonding at the seams 82,83,84 are accomplishedautomatically by heat sealing. Moreover the bonding or seaming may beaccomplished by using vibrations to effect the bonds in making this typeof product. The envelope can be decorated as desired.

In effecting heat seals electrically heated bars are used, for example.The heat seals are effected in two to three seconds at a pressure ofabout 2 kg/cm² at a temperature from about 200° to about 220°C. Thecurrent pulses are applied to the bars at a rate of about 0.2 seconds toabout one second with a current value from about 20 to 30 amperes. Thestrength of the heat seals increases from about one second ofapplication of heat to about two seconds and longer application of heatdoes not improve the strength of the seal materially.

Ultrasonic heat sealing is accomplished in about two to three secondswhen the vibratory cycle is about 28 Kc. Furthermore heat sealing byusing induction or resistance heating of the sealing elements ispossible.

The synthetic paper can be used as packaging and wrapping paper. FIG. 10illustrates a roll 90 of synthetic paper 91 made according to theinvention for wrapping an item 92. Those skilled in the art willunderstand that the item 92 can be a box or package to be wrapped or canbe an article of food, or any article or articles such as a stack ofcards or papers to be wrapped, for example automatically. The syntheticpaper 91 can likewise be decorated as desired.

As indicated heretofore a particular advantage of the paper-likelaminate according to the invention is that it is waterproof and can befolded and unfolded thousands of times without failure or rupture. Thisfeature makes it possible to make maps and charts having a long lifewhen subjected to moisture and folding and unfolding. The waterproofcharacteristics of the synthetic paper of the invention improve its useas a wall covering.

The synthetic paper can be used to make wallpaper 95 illustrated in FIG.11. The wallpaper may be embossed as illustrated at 96 or may have anydesired decorations, including printing, thereon.

Those skilled in the art will understand that laminates formed (18examples) according to Table I(a) through Table IV have properties asset forth in Table V which are generally superior to those of naturalcellulose paper. Some effects of filler on a PP base layer can be seenfrom Table VI. It can be seen from the latter table that in order tomaintain good mechanical strength in the base layer the fillerpreferably should not exceed 20% by weight of the base layercomposition.

The properties of PP compositions (17 examples) with filler therein asnoted are set forth in Tables VII(a) and VII(b) and the propertiesdesignated A and B are generally superior to natural cellulose paper.

Those skilled in the art will recognize that microvoid formation isessential to the paper-like layer of the present invention and thesemicrovoids are elongated and formed in dependence upon the extent ofstretching and the size of the particles of the filler whose diameterprincipally determines the major width dimension of the voids. Thenumber of microvoids developed is principally controlled by thepercentage, by weight, of filler in the paper-like layer compositions.The length of the voids is essentially controlled by the extent of thestretching and this is designated (x) in the various tables.

Thus the paper-like layers of the various laminates disclosed arefibrous internally and are able to have images printed thereon andaccept various inks and can be written on by various instruments.

The synthetic paper according to the invention has excellent tear andburst strength and the heat seals or bonding of seams likewise are ofgreat strength. Hot wet adhesives or any type of suitable adhesive canlikewise be used to make suitable bonds.

It can be seen that the principal constituents in the paper are theresins and the filler components. The stabilizers are only from about0.1% to 2% by weight; the antistatic agents are about 0.1% to about 0.5%by weight; the latter value is true for the dispersion agents and theanti-ultraviolet degradation agents. The synthetic paper according tothe invention can be made without the additional components, those otherthan the principal components, listed above.

While preferred embodiments of the invention have been shown anddescribed it will be understood that many modifications and changes canbe made within the true spirit and scope of the invention.

What we claim and desire to secure by letters patent is:
 1. A method ofproducing a synthetic paper-like laminate comprising, providing a basefilm layer made of a thermoplastic resin, uniaxially orienting the basefilm layer, laminating on said base film layer a paper-like film layermade of a thermoplastic resin having more than 25% and no more than 65%by weight of particles of a fine inorganic filler substantiallyuniformly distributed therein thereby to form a laminate, the weightpercentage of said inorganic filler being dependent on the weight of theresin plus the filler, stretching while in a heated state the laminatein a transverse direction to biaxially orient the base film layer anduniaxially orient the paper-like film layer including stretching thelaminate in the transverse direction from 7 to 16 times greater than theoriginal transverse dimension of said films in the last-mentioneddirection to develop microvoids having a void proportion of from 10% to65% in said paper-like film layer in conjunction with said particles offiller distributed internally in the paper-like layer as comminicatingand independent microvoids to develop fibrous-like portions of the resinthereof among the microvoids interiorly of said paper-like film layer todefine therein a cellular, fibrous structure, said stretching includingdeveloping of microvoids open to the surface of said paper-like filmlayer free of said base film layer and distributed throughout saidsurface, ceasing said stretching, and setting said resin afterstretching maintaining the internal microvoids including thelast-mentioned microvoids open to said surface upon cessation of saidstretching.
 2. A method of producing a synthetic paper-like laminateaccording to claim 1, including applying an electrostatic charge to saidsynthetic laminate to render said paper-like layer more attractive toink.
 3. A method of producing a synthetic paper-like laminate accordingto claim 1, in which said base film layer is extruded, cooledimmediately afterward and stretched while in a heated state in alongitudinal direction to orient the resin thereof.
 4. A method ofproducing a synthetic paper-like laminate according to claim 1, in whichsaid laminate is preheated and then stretched transversely to biaxiallyorient the base film layer and uniaxially orient the paper-like filmlayer.